How do I figure out if Some qualified dividends or section 199A dividends are from securities that didn't meet the required holding period?

To answer this question, refer to IRS Tax Cuts and Jobs Act, Provision 11011 Section 199A - Qualified Business Income Deduction FAQs

Ineligible dividends include those for which the taxpayer did not meet holding period requirements.  The QBID may not be taken for any dividend reported in box 5 for dividends received on a share of ...stock that is held for 45 days or less during the 91-day period beginning on the date that is 45 days before the date on which such share became ex-dividend with respect to the dividend. When counting the number of days that the stock is held, include the day the stock is disposed of but not the day the stock is acquired. Also, don't count days during which the risk of loss was diminished. Specifically, don't count any day during which any of the following conditions are met:

1. The taxpayer had an option to sell, was under a contractual obligation to sell, or entered into (and not closed) a short sale of substantially identical stock or securities.
    
2. The taxpayer was a grantor (writer) of an option to buy substantially identical stock or securities.
    
3. The taxpayer's risk of loss was diminished by holding one or more other positions in substantially similar or related property.

In addition, the deduction may not be taken for any dividend on shares of the stock reported in box 5 to the extent the taxpayer is under an obligation (whether pursuant to a short sale or otherwise) to make related payments with respect to positions in substantially similar or related property.